The present invention relates to a nonrecorded section detection system in a tape recorder apparatus.
The nonrecorded section detection system is very useful because it can select a desired program within plural programs recorded on a magnetic tape in a tape recorder apparatus. The nonrecorded section detection system usually functions to feed the magnetic tape at a fast speed upon depression of a nonrecorded section detection switch and stop the tape feed or feed the magnetic tape at a normal playback speed upon detection of a nonrecorded section provided before the desired program. Thereafter the tape recorder apparatus is automatically placed in its normal playback mode or manually placed in its normal playback mode through the use of a playback button, thereby reproducing the desired program in the normal playback mode.
The nonrecorded section detection system usually comprises a nonrecorded section detection head, a nonrecorded section detection circuit and a tape drive control mechanism including a driving transistor controlled by a nonrecorded section detection signal derived from the nonrecorded section detection circuit. The conventional nonrecorded section detection system further comprises a differentiation circuit including a capacitor connected to receive the nonrecorded section detection signal derived from the nonrecorded section detection circuit and a resistor interposed between a DC power source and said capacitor. The driving transistor of the tape drive control mechanism is controlled by a differentiated output signal of the differentiation circuit, thereby activating a plunger for releasing the nonrecorded section detection mode.
In the above-mentioned conventional nonrecorded section detection system, there is a possibility that the driving transistor is erroneously triggered into conduction when a power supply switch is closed or opened. This will activate the plunger and, hence, the tape feed mechanism is shifted when it is not desired.
There have been proposed some approaches to prevent the above-mentioned erroneous operation occurring when the power switch is closed. However, the conventional approaches are not effective at all times.